FIG. 1 is a view showing the configuration of a conventional radio communication system. 1 indicates a cellular phone functioning as a personal digital assistant (or a portable information terminal). 2 to 6 indicate a plurality of fixed terminals such as dispensers respectively. The fixed terminals 2 to 6 are disposed in a peripheral area of the cellular phone 1.
Next, an operation will be described below.
For example, a user operates the fixed terminal 2 by using the cellular phone 1, the cellular phone 1 and the fixed terminal 2 are connected with each other through a link of a bluetooth system.
In detail, when the establishment of a link of the bluetooth system is desired, as shown in FIG. 2, an address request signal called “inquiry” is output from the cellular phone 1.
When the address request signal output from the cellular phone 1 is received in the fixed terminal 2, a device address peculiar to the fixed terminal 2 is returned from the fixed terminal 2 to the cellular phone 1 as an “inquiry response”.
In the cellular phone 1, when the peculiar device address returned from the fixed terminal 2 is received, a page sequence prescribed by a specification of the bluetooth system is performed to acknowledge a device address of the cellular phone 1 and the device address of the fixed terminal 2, and a link between the cellular phone 1 and the fixed terminal 2 is established.
Also, in addition to the above-described prior art, a technique for using a new device for a radio local area network is disclosed in Published Unexamined Japanese Patent Application No. 2000-224197.
However, this technique merely relates to the structuring of the radio local area network and differs from the technique for connecting two devices with each other through the bluetooth system.
Because the conventional radio communication system has the above-described configuration, after the address request signal is output from the cellular phone 1, the cellular phone 1 is required to wait for the device address sent from the fixed terminal 2. Therefore, a problem has arisen that it is impossible to rapidly establish a link of the bluetooth system between the cellular phone 1 and the fixed terminal 2.
Also, in addition to the fixed terminal 2, when the other fixed terminals 3 to 6 send device addresses to the cellular phone 1 respectively in response to the address request signal, the cellular phone 1 is required to select a desired fixed terminal to be connected with the cellular phone 1. Therefore, a time required to establish a link of the bluetooth system is further prolonged.
The present invention is provided to solve the above-described problem, and the object of the present invention is to provide a personal digital assistant, a radio communication system and a link establishing method for rapidly establishing a link of the bluetooth system.